Investigation into the genetic diversity of certain endangered native breeds of domestic animals has been in common practice for several decades. The primary objective of these investigations has been to reveal the exceptional genetic value of such breeds, both for their conservation and also to gain insight into their current genetic status, as they have been undergoing a progressive decrease in population size and general diversity; this has been compounded by the general lack of an optimal breeding scheme. In this study, we have investigated changes in the genetic diversity of six Hungarian local chicken breeds based on 29 microsatellite loci over a period of 15 years. In terms of the basic diversity measures, populations sampled in 2017 generally exhibited a lower heterozygosity and mean number of alleles and thus, experienced a higher degree of inbreeding. Although the effective population size increased, the estimates of populations sampled over different periods indicated comparatively low values, suggesting overall lower genetic variance. Pairwise FST estimates were higher in the populations sampled in 2017, showing a larger genetic distance between them. Considerable differences exist between the populations of the same breeds, which can most likely be attributed to genetic drift. STRUCTURE results have shown a clear separation between the Hungarian populations, which is in agreement with the principal coordinate analysis. The most likely clustering was found at K = 6, classifying the populations of the same breed as one group. No considerable allele loss was found in the Hungarian indigenous chicken breeds after 15 years of conservation. In general terms, after 15 years, the level of inbreeding within the populations was, in fact, higher, although this could be effectively reduced through the use of an improved mating system. Consequently, the breed management applied in the case of Hungarian local chicken breeds was found to be effective at adequately conserving their genetic variability.